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The task of a first principles theoretical calculation of the rate of gas–liquid nucleation has remained largely incomplete despite the existence of reliable results from unbiased simulation studies at large supersaturation. Although the classical nucleation theory formulated by Becker–Doring–Zeldovich about a century ago provides an elegant, widely used picture of nucleation in a first-order phase transition, the theory finds difficulties in predicting the rate accurately, especially in the case of gas-to-liquid nucleation. Here, we use a multiple-order parameter description to construct the nucleation free energy surface needed to calculate the nucleation rate. A multidimensional non-Markovian (MDNM) rate theory formulation that generalizes Langer's well-known nucleation theory by using the Grote–Hynes MDNM treatment is used to obtain the rate of barrier crossing. We find good agreement of the theory with the rate obtained by direct unbiased molecular dynamics simulations—the latter is feasible at large supersaturation, S. The theory gives an experimentally strong dependence of the rate of nucleation on supersaturation, S. Interestingly, we find a strong influence of the frequency-dependent friction coefficient at the barrier top. This arises from multiple recrossings of the barrier surface. We find that a Markovian theory, such as Langer's formulation, fails to capture the rate quantitatively. In addition, the multidimensional transition state theory expression performs poorly, revealing the underlying role of the friction coefficient. [ABSTRACT FROM AUTHOR]

Nanoconfined poly(4-methylstyrene) [P(4-MS)] films exhibit reductions in glass transition temperature (Tg) relative to bulk Tg (Tg,bulk). Ellipsometry reveals that 15-nm-thick P(4-MS) films supported on silicon exhibit Tg − Tg,bulk = − 15 °C. P(4-MS) films also exhibit fragility-confinement effects; fragility decreases ∼60% in going from bulk to a 20-nm-thick film. Previous research found that incorporating 2–6 mol % 2-ethylhexyl acrylate (EHA) comonomer in styrene-based random copolymers eliminates Tg- and fragility-confinement effects in polystyrene. Here, we demonstrate that incorporating 3 mol % EHA in a 4-MS-based random copolymer, 97/3 P(4-MS/EHA), eliminates the Tg- and fragility-confinement effects. The invariance of fragility with nanoconfinement of 97/3 P(4-MS/EHA) films, hypothesized to originate from the interdigitation of ethylhexyl groups, indicates that the presence of EHA prevents the free surface from perturbing chain packing and the cooperative mobility associated with Tg. This method of eliminating confinement effects is advantageous as it relies on the simplest of polymerization methods and neat copolymer only slightly altered in composition from homopolymer. We also investigated whether we could eliminate the Tg-confinement effect with low levels of 2-ethylhexyl methacrylate (EHMA) in 4-MS-based or styrene-based copolymers. Although EHMA is structurally nearly identical to EHA, 4-MS-based and styrene-based copolymers incorporating 4 mol % EHMA exhibit Tg-confinement effects similar to P(4-MS) and polystyrene. These results support the special character of EHA in eliminating confinement effects originating at free surfaces. [ABSTRACT FROM AUTHOR]

Many methods to accelerate sampling of molecular configurations are based on the idea that temperature can be used to accelerate rare transitions. These methods typically compute equilibrium properties at a target temperature using reweighting or through Monte Carlo exchanges between replicas at higher temperatures. A recent paper [G. M. Rotskoff and E. Vanden-Eijnden, Phys. Rev. Lett. 122, 150602 (2019)] demonstrated that accurate equilibrium densities of states can also be computed through a nonequilibrium "quench" process, where sampling is performed at a higher temperature to encourage rapid mixing and then quenched to lower energy states with dissipative dynamics. Here, we provide an implementation of the quench dynamics in LAMMPS and evaluate a new formulation of nonequilibrium estimators for the computation of partition functions or free energy surfaces (FESs) of molecular systems. We show that the method is exact for a minimal model of N-independent harmonic springs and use these analytical results to develop heuristics for the amount of quenching required to obtain accurate sampling. We then test the quench approach on alanine dipeptide, where we show that it gives an FES that is accurate near the most stable configurations using the quench approach but disagrees with a reference umbrella sampling calculation in high FE regions. We then show that combining quenching with umbrella sampling allows the efficient calculation of the free energy in all regions. Moreover, by using this combined scheme, we obtain the FES across a range of temperatures at no additional cost, making it much more efficient than standard umbrella sampling if this information is required. Finally, we discuss how this approach can be extended to solute tempering and demonstrate that it is highly accurate for the case of solvated alanine dipeptide without any additional modifications. [ABSTRACT FROM AUTHOR]

The fragility of glass describes how rapidly its molecules slow down as it is cooled near its glass transition temperature. In nanoscale films, polymer glasses with higher fragility experience larger reductions in their Tg compared to those with lower fragility. We investigated whether this is due to the free surface of the polymers, which can cause the surface Tg (Tgsurf) to decrease relative to the bulk Tg. By measuring Tgsurf of various polymers, we found that the shift in Tgsurf relative to the bulk Tg increased with fragility. This suggests that more fragile polymers are more susceptible to the free surface effect. We explain this using the concept of energy landscape, as it is used to explain the different slowdown rates between strong and fragile glass formers at Tg. [ABSTRACT FROM AUTHOR]

How to fabricate perpendicularly oriented domains (PODs) of lamellar and cylinder phases in block copolymer thin films remains a major challenge. In this work, via a coarse-grained molecular dynamics simulation study, we report a solvent evaporation strategy starting from a mixed solution of A-b-B-type diblock copolymers (DBCs) and single-chain nanoparticles (SCNPs) with the same composition, which is capable of spontaneously generating PODs in drying DBC films induced by the interface segregation of SCNPs. The latter occurs at both the free surface and substrate and, consequently, neutralizes the interface selectivity of distinct blocks in DBCs, leading to spontaneous formation of PODs at both interfaces. The interface segregation of SCNPs is related to the weak solvophilicity of the internal cross-linker units. A mean-field theory calculation demonstrates that the increase in the chemical potential of SCNPs in the bulk region drives their interface segregation along with solvent evaporation. We believe that such a strategy can be useful in regulating the PODs of DBC films in practical applications. [ABSTRACT FROM AUTHOR]

Thermocapillary convection was investigated in a metallic system of pure Ni, at the nanoscale, by molecular dynamics. The system interface was irradiated by a heat flux, mimicking a focused laser source. The melt pool was submitted to a large temperature gradient that modified the surface tension along the interface. In liquid metal, because surface tension typically decreases with increasing temperature, the result is a gradient of surface tension along the free surface. The liquid metal, therefore, started to flow in the direction of high surface tension. Two counter-rotating convection cells developed, characteristic of those observed in welding and other material processing. A systematic estimation of relevant parameters in hydrodynamics allowed us to interpret the results in terms of Prandtl, Marangoni, and Péclet numbers. This study demonstrates the influence of laser power and system size on pool shape and flow characteristics. [ABSTRACT FROM AUTHOR]

We evaluate neural network (NN) coarse-grained (CG) force fields compared to traditional CG molecular mechanics force fields. We conclude that NN force fields are able to extrapolate and sample from unseen regions of the free energy surface when trained with limited data. Our results come from 88 NN force fields trained on different combinations of clustered free energy surfaces from four protein mapped trajectories. We used a statistical measure named total variation similarity to assess the agreement between reference free energy surfaces from mapped atomistic simulations and CG simulations from trained NN force fields. Our conclusions support the hypothesis that NN CG force fields trained with samples from one region of the proteins' free energy surface can, indeed, extrapolate to unseen regions. Additionally, the force matching error was found to only be weakly correlated with a force field's ability to reconstruct the correct free energy surface. [ABSTRACT FROM AUTHOR]

This article proposes two contributions to the calculation of free‐surface flows using the particle finite element method (PFEM). The PFEM is based upon a Lagrangian approach: a set of particles defines the fluid and each particle is associated with a velocity vector. Then, unlike a pure Lagrangian method, all the particles are connected by a triangular mesh. The difficulty lies in locating the free surface from this mesh. It is a matter of deciding which of the elements in the mesh are part of the fluid domain, and to define a boundary—the free surface. Then, the incompressible Navier–Stokes equations are solved on the fluid domain and the particle position is updated using the velocity vector from the finite element solver. Our first contribution is to propose an approach to adapt the mesh with theoretical guarantees of quality: the mesh generation community has acquired a lot of experience and understanding about mesh adaptation approaches with guarantees of quality on the final mesh. The approach we use here is based on a Delaunay refinement strategy, allowing to insert and remove nodes while gradually improving mesh quality. We show that what is proposed allows to create stable and smooth free surface geometries. One characteristic of the PFEM is that only one fluid domain is modeled, even if its shape and topology change. It is nevertheless necessary to apply conditions on the domain boundaries. When a boundary is a free surface, the flow on the other side is not modeled, it is represented by an external pressure. On the external free surface boundary, atmospheric pressure can be imposed. Nevertheless, there may be internal free surfaces: the fluid can fully encapsulate cavities to form bubbles. The pressure required to maintain the volume of those bubbles is a priori unknown. For example, the atmospheric pressure would not be sufficient to prevent the bubbles from deflating and eventually disappearing. Our second contribution is to propose a multi‐point constraint approach to enforce global incompressibility of those empty bubbles. We show that this approach allows to accurately model bubbly flows that involve two fluids with large density differences, for instance water and air, while only modeling the heavier fluid. [ABSTRACT FROM AUTHOR]

We consider the viscous incompressible fluids in a three-dimensional horizontally periodic domain bounded below by a fixed smooth boundary and above by a free moving surface. The fluid dynamics are governed by the Navier-Stokes equations with the effect of gravity and surface tension on the free surface. We develop a global well-posedness theory by a nonlinear energy method in low regular Sobolev spaces with several techniques, including: the horizontal energy-dissipation estimates, a new tripled bootstrap argument inspired by Guo and Tice [Arch. Ration. Mech. Anal. (2018)]. Moreover, the solution decays asymptotically to the equilibrium in an exponential rate. • The global well-posedness has been proved in lower regularity space. • The asymptotic stability has been proved around the equilibrium. • The exponential decay of energy has been proved. [ABSTRACT FROM AUTHOR]

This article details the development and evaluation of a novel wave energy converter (WEC) aimed at efficiently capturing wave energy for electricity production. The study employs Computational Fluid Dynamics (CFD) techniques, specifically the URANS method and the k-ω SST turbulence model, to solve the Navier-Stokes equations and capture the free surface using the Volume of Fluid (VOF) model. The CFD results are validated against experimental data to ensure accuracy. Various design parameters of the proposed device were tested, revealing that the arms and bottom angle significantly affect its performance. Unlike the floating Wave Dragon (WD) device, which utilises potential energy and is set in deep water, the new fixed-seabed device is positioned in the transitional wave region near the shore, where waves retain 80% of their energy. It can be constructed from environmentally friendly cement, making it resistant to hurricanes and suitable for any wave turbine in the open sea. The MP687 turbine was used to capture the wave energy in the proposed device, testing its performance in three positions: in the open sea, in the middle of the device, and at the device's outlet. The results show that the device significantly enhances wave energy concentration, especially when the turbine is placed at the outlet. The proposed device offers numerous advantages, including its fixed position in a high-energy wave zone, the efficient use of turbulent kinetic energy, and robust construction that can withstand storms. [ABSTRACT FROM AUTHOR]

The primary function of composite vertical breakwaters is to shield harbor basins from incoming waves and currents. To ensure high hydraulic efficiency, recurved parapets are commonly employed to mitigate the wave overtopping phenomenon. However, these breakwaters are typically used in locations characterized by high water depth. In such settings, nonbreaking waves form on the seaward side of the structure, leading to a phenomenon known as "Confined-Crest Impact" (referred to as "C-CI" hereafter). This phenomenon arises from the interaction between nonbreaking waves and overhanging structures. As presented in previous research works, the same author showed a method for considering the pressure increment induced by the "C-CI" using empirical relationships. However, these tools were unable to predict pressure increments in the presence of submerged berms. Nevertheless, vertical breakwaters commonly feature a berm designed primarily for seabed leveling. Particularly in areas with deep seabeds, the berm serves the purpose of diminishing the caisson height. The presence of the berm amplifies shoaling effects, leading to an increase in free surface velocity and, consequently, a rise in excess pressure induced by the "C-CI" in the presence of a recurved parapet. For this reason, this research specifically focuses on investigating the influence of the toe berm on "C-CI." A series of computational fluid dynamics (CFD) numerical simulations have been conducted to analyze how changing the height of the toe berm affects the loading conditions on the recurved parapet. The geometrical configuration of the toe berm has been selected based on the "Parameter Map" outlined in the PROVERBS manual. As a main result, the intensity of "C-CI" tends to increase as the height of the toe berm increases. This is mainly due to the shoaling effect induced by the berm, as the steepness of the waves increases. A new empirical formula has been developed, with the purpose of determining the coefficient required to apply in Goda's formulas, enabling the estimation of pressure distribution along the structure in presence of berms. [ABSTRACT FROM AUTHOR]

There are few studies on the effects of spatial distribution of hydrodynamics on the micro-mixing in stirred reactors. In this work, a statistical approach is introduced to quantitatively assess the spatial distributions of hydrodynamic parameters, using the turbulent dissipation rate as an example. According to the results, the effects of impeller geometry and angular velocity on the turbulent dissipation rate can be well described in terms of the volume-averaged values and spatial distribution functions. In the present study, a more uniform distribution of the turbulent dissipation rate is achieved by the multiple impellers with an inclinational angle of 15° at the same rotational speed. However, increasing the inclinational angle can decrease the volume-averaged value. The cumulative percentage of area-averaged turbulent dissipation rate is well modeled by an exponential function. The effects of impeller types on the meso- and micro-mixing processes are also investigated. It is found that the micro-mixing process has more significant influences than the meso-mixing process in the bottom region and near the free surface. The effects of impeller types on the micro-mixing performance are further investigated using the Villermaux–Dushman reaction system, both experimentally and numerically. An empirical correlation that considers the spatial distribution of turbulent parameters for the reaction rate of I2 synthesis is proposed. The results show that the predictions of segregation index, which represents micro-mixing performance, are improved by a numerical model coupled with the new reaction rate model. [ABSTRACT FROM AUTHOR]

In this article, the performances of the SPH method to solve Shallow Water Equations SWEs with three investigation parameters were studied, such as the type of kernel functions, namely: cubic spline, Gaussian and quintic spline kernels, the number of particles used and the stabilization terms injected, specifically: Lax Friedrichs flux, artificial viscosity and two shocks Riemann solver. Three benchmarking tests make the subject of unsteady free surface flow in this study. It is 1D typical dam-break on wet and dry bottom; 2D partial dam-break on a dry floodplain and 2D partial dam-break on channel with 90° bend. The analysis of the different errors between the numerical and analytical solutions and/or the experimental data shows that the SPH method gives reliable values with the selected optimal parameters which are the cubic kernel function and the artificial viscosity term. The increase in the number of particles increases the precision but also the calculation time. [ABSTRACT FROM AUTHOR]

This paper presents an analytical investigation of the solutions to a control-volume model for liquid films flowing down a vertical fibre. The evolution of the free surface is governed by a coupled system of degenerate nonlinear partial differential equations, which describe the fluid film's radius and axial velocity. We demonstrate the existence of weak solutions to this coupled system by applying a priori estimates derived from energy-entropy functionals. Additionally, we establish the existence of traveling wave solutions for the system. To illustrate our analytical findings, we present numerical studies that showcase the dynamic solutions of the partial differential equations as well as the traveling wave solutions. [ABSTRACT FROM AUTHOR]

We aim to investigate the flow of an ethylene glycol-based hybrid nanofluid over a horizontal surface with a free stream velocity. To assess the viscosity and thermal conductivity of nanoparticles with various shapes, we employed the Brinkman, Timofeeva, and Yamada Ota unit cell models. The study explores heat transfer in the flow system considering the effects of viscous and ohmic dissipations, linear radiative heat flux, and heat generation under convective boundary conditions. A non-similar system is developed using appropriate non-similarity transformations up to the third-level truncation and numerically solved using the bvp4c algorithm. The novelty of the proposed model lies in obtaining the non-similar solution and incorporating the Brinkman, Timofeeva, and Yamada Ota unit cell models. The results indicated that the Brinkman viscosity model resulted in an increase in the wall heat transfer rate with a rise in particle volume fraction. It is also inferred that platelet-shaped nanoparticles exhibit a significantly higher heat transfer rate compared to spherical-shaped nanoparticles. [ABSTRACT FROM AUTHOR]

AbstractThe primary objective of the current work is to establish the impacts of planar boundary and non-planar boundary on the displacement components (DCs) of Rayleigh-type wave propagation in an elastic structure. The elastic structure, precisely, incorporates a pre-stressed nearly incompressible elastic material in the half-space along with the non-planar boundary at the free surface. The methodology applied features variable separable technique and Taylor’s series expansion along with substitution method to establish the expressions for DCs and frequency relation. The frequency relation of Rayleigh-type wave is obtained for the situation considering planar free surface, which is further reduced as a special case of the study and validated with the classical result present in the literature. The DCs of Rayleigh-type wave have been numerically computed, and their reliance on wave number have been exhibited graphically. In addition to this, the influences of affecting parameters viz., hydrostatic stress, principal Cauchy stress and curvature parameter on DCs have been traced out. The computational result also manifests the domain of existence of Rayleigh-type wave propagating in the considered model in the presence of planar free surface. [ABSTRACT FROM AUTHOR]

The 2023 M7.8 and M7.5 earthquake doublet near Kahramanmaraş, Turkey, provides insight regarding how large earthquakes rupture complex faults. Here we determine the faults geometry using surface ruptures and Synthetic Aperture Radar measurements, and the rupture kinematics from the joint inversion of high-rate Global Navigation Satellite System (GNSS), strong-motion waveforms, and GNSS static displacement. The M7.8 event initiated on a splay fault and subsequently propagated along the main East Anatolian Fault with an average rupture velocity between 3.0 and 4.0 km/s. In contrast, the M7.5 event demonstrated a bilateral supershear rupture of about 5.0–6.0 km/s over an 80 km length. Despite varying strike and dip angles, the sub-faults involved in the mainshock are nearly optimally oriented relative to the local stress tensor. The second event ruptured a fault misaligned with respect to the regional stress, also hinting at the effect of local stress heterogeneity in addition to a possible free surface effect. The February 2023 Kahramanmaraş earthquake doublet reveals how pre-stress and local stress heterogeneity influence fault ruptures, with key insights into rupture kinematics, fault geometry, and stress interactions along complex fault systems. [ABSTRACT FROM AUTHOR]

The route to chaos and the phase dynamics of the large scales in a rotating shallow-water model have been rigorously examined through the construction of an autonomous five-mode Galerkin truncated system employing complex variables, useful in investigating how large/meso-scales are destabilized and how their dynamics evolves and transits to chaos. This investigation revealed two distinct transitions into chaotic behaviour as the level of energy introduced into the system was incrementally increased. The initial transition manifests through a succession of bifurcations that adhere to the established Feigenbaum sequence. Conversely, the subsequent transition, which emerges at elevated levels of injected energy, is marked by a pronounced shift from quasi-periodic states to chaotic regimes. The genesis of the first chaotic state is predominantly attributed to the preeminence of inertial forces in governing nonlinear interactions. The second chaotic state, however, arises from the augmented significance of free surface elevation in the dynamical process. A novel reformulation of the system, employing phase and amplitude representations for each truncated variable, elucidated that the phase components present a temporal piece-wise locking behaviour by maintaining a constant value for a protracted interval, preceding an abrupt transition characterised by a simple rotation of ±π, even as the amplitudes display chaotic behaviour. It was observed that the duration of phase stability diminishes with an increase in injected energy, culminating in the onset of chaos within the phase components at high energy levels. This phenomenon is attributed to the nonlinear term of the equations, wherein the phase components are introduced through linear combinations of triads encompassing disparate modes. When the locking durations vary across modes, the resultant dynamics is a stochastic interplay of multiple π phase shifts, generating a stochastic dynamic within the coupled phase triads, observable even at minimal energy injections. [ABSTRACT FROM AUTHOR]

The plasma electrolytic polishing (PEP) process on Q235 low-carbon steel anode in (NH4)2SO4 electrolyte was investigated, and its surface properties under different PEP conditions were evaluated. The surface roughness of PEP samples under different electrolyte concentrations, initial roughness, voltages and treating times were measured. The surface morphologies and compositions of typical PEP samples were analyzed, and their wettability and surface free energy under different polishing times were evaluated. It was found that the near-surface temperature of the steel sample raised quickly with increasing the voltage, and then remained at about 100°C after 200V, which is beneficial to keep the microstructure and mechanical properties of Q235 low-carbon steel. Under the parameters of 3.0wt.% (NH4)2SO4 aqueous solution and applied voltage of 200V, the 8min PEP treatment could reduce the surface roughness of Q235 low-carbon steel from 2.100μm to 0.437μm. In addition, the polishing efficiency was the highest in the initial PEP stage, meanwhile, it also increased with the increase of initial roughness of the sample. After the PEP treatment, the contact angle of water on low-carbon steel decreased, and its surface free energy was slightly reduced. Moreover, the thickness of natural oxide film on Q235 low-carbon steel was reduced by about 30% after 8 min polishing treatment. [ABSTRACT FROM AUTHOR]

In order to improve the water hole blasting effect in the water rich rock area of a certain open pit mine, a study was conducted on rock debris filling materials through theoretical analysis and on site experiments. The influence of radial water uncoupling charge coefficient, filling length, and delayed detonation on the blasting effect was analyzed through numerical simulation. The results show that as the particle size of rock debris increases, the shear strength of the filling structure also increases, and the effect of filling is also enhanced; The filling effect is most significant when the ratio of <5 mm with $5 mm rock debris particles is 3 5 7 in the filling structure; When the radial water uncoupled charge coefficient Kd is 1. 33, perfect blasting effects can be achieved to save explosive costs;Delayed detonation can provide more free surfaces to reduce the fragmentation of rock masses. [ABSTRACT FROM AUTHOR]

This paper reports the results of thermal spallation experiments on specially dried shale samples with 3 bedding orientations (0°, 45° and 90°) under 3 flame temperatures (899 °C, 1243 °C and 1559 °C) and the 3D thermal elastic finite element modelling. Under open flame heating, continuous spallation is observed with ejection of various spalls and popping sounds. After a period of spallation, tensile fractures are formed in the samples and grow perpendicular to the heating surface, except for a sample with bedding orientation of 90° under the low temperature. Increasing flame temperature promotes ejection, popping sounds and spallation rate, but reduces the spallation starting time, spallation duration, depression diameter and depression depth. The model shows that heating induces compressive stress in the surface layer and tensile stresses beneath it. The tensile stress is found to be sufficient to generate large tensile fractures. The ratio between the induced compressive and tensile stresses increases with increasing spallation depth but little affected by the flame temperature. The spallation compressive stress increases with temperature from 29 to 51% of the uniaxial compressive strength. This stress is shown to be sufficient to cause buckling of thin layers separated from the bulk of the rock. The size of the buckling layer is smaller than the size of the spallation zone leading to a mosaic pattern seen on the surface after spallation. The results are important for further understanding of the mechanism of thermal spallation of rocks as well as large scale spallation-like processes in the Earth's crust. [ABSTRACT FROM AUTHOR]

Improving the durability of short-rotation wood can be achieved through chemical and thermal modification. Chemical and thermal modification can have an impact on the physicochemical properties of wood, which can affect wood's surface characteristics and its resistance to weathering. The purpose of this study was to investigate the surface characteristics and artificial weathering resistance of chemically and thermally modified short-rotation teak wood coated with linseed oil (LO)-, tung oil (TO)-, and commercial oil-based coatings consisting of a mixture of linseed oil and tung oil (LT) and commercial oil-based polyurethane resin (LB) coatings. The short-rotation teak woods were prepared in untreated and treated with furfuryl alcohol (FA), thermal treatment (HT) at 150 and 220 °C, and combination of glycerol–maleic anhydride (GMA) impregnation with thermal treatment at 150 and 220 °C. The surface characteristics measured were surface free energy, wettability, Persoz hardness, bonding quality, and color changes before and after artificial weathering exposure. The results showed that chemical and thermal modifications treatment tended to reduce total surface free energy (SFE), hardness, wettability, and bonding quality. FA and GMA at 220 °C treatments provided homogenization effect on surface characteristics, especially in total SFE and wettability. The total SFE of untreated wood ranged from 45.00 to 51.13 mN/m, and treated wood ranged from 40.58 to 50.79 mN/m. The wettability of oil-based coating according to K-value ranged from 0.20 to 0.54. TO presented better photostability than LO. Short-rotation teak wood coated with oil-based commercial coatings presented better weathering resistance compared to pure natural drying oil. Commercial oil-based coatings provided better weathering protection for the chemically and thermally modified teak wood. The application of oil-based coatings on chemically and thermally modified short-rotation teak is being considered for the development of a better wood-protection system. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of airborne particle abrasion with different particles on the surface free energy, roughness, and biaxial flexural strength of a feldspathic ceramic by comparing it with hydrofluoric acid etching, the standard surface treatment, and polishing. Square-shaped feldspathic ceramic specimens (12 mm × 12 mm × 1.2 mm) were divided into subgroups as airborne particles abraded with alumina (AO3a, AO3b, AO25, AO50a, AO50b, AO90, AO110a, AO110b, AO120a, and AO120b), silica (SO50a, SO50b, SO100, and SO100/200), or nutshell granule (NS100/200), hydrofluoric acid etched, and polished (n = 12). Surface free energy (n = 5), roughness (n = 5), biaxial flexural strength (n = 12), and Weibull moduli (n = 12) were investigated. Data were evaluated with 1-way ANOVA and Tukey HSD tests, and possible correlations were investigated with Pearson's correlation (α = 0.05). SO100/200 mostly had lower surface free energy (p ≤ 0.011), and polishing and etching led to higher surface free energy than AO3a, AO3b, and AO120a (p ≤ 0.031). Polished, SO100, and SO50b specimens mostly had lower roughness and AO125 had the highest roughness (p ≤ 0.029). SO100/200 mostly had lower biaxial flexural strength (p ≤ 0.041), and etched specimens had higher biaxial flexural strength than AO120a, AO120b, and SO50b (p ≤ 0.043). AO3b had the highest (33.56) and AO120b had the lowest (11.8) Weibull modulus. There was a weak positive correlation between the surface free energy and the biaxial flexural strength (r = 0.267, p = 0.011). A larger particle size mostly resulted in higher roughness, which was also affected by the particle shape. Most of the test groups had similar biaxial flexural strength to that of the hydrofluoric acid-etched group. Therefore, for tested feldspathic ceramic, airborne particle abrasion with tested parameters may be a suitable alternative without causing any further damage. [ABSTRACT FROM AUTHOR]

In this paper, free surface problems of Stefan type for the parabolic heat equation are considered. The analytical solutions of the problems are based on the method of heat polynomials and integral error function in the form of series. Convergence of the series solution is considered and proved. Both one-and two-phase Stefan-type problems are investigated. Numerical results for one-phase inverse Stefan problem are presented and discussed. [ABSTRACT FROM AUTHOR]

In this paper, to determine the efficacy of the porous bed on damping far-field wave energy, the wave dynamics around a circular plate is studied. By combining the appropriate boundary conditions, the unknown potential is attained for the free surface and the plate-covered region. The Bessel series solution is attained further, by employing the matched eigenfunction expansion technique. Wave force excitation on the circular plate, deflection of the plate, and flow distribution is calculated and examined to comprehend the efficacy of the current investigation. Moreover, the motion of the plate is assessed in the time domain. The study reveals a substantial reduction in wave amplitude on the plate's leeward side because of the energy dissipation by the porous bed. Also the study concludes that for intermediate values of porosity with larger wavenumbers, approximately 50% of wave power is dissipated with respect to incident wave power. [ABSTRACT FROM AUTHOR]

Heat exchangers can be coated with functional layers to reduce the negative effects of established fouling films. In the process, long-term layer stability is a requirement for the fouling-inhibiting properties of the surface coatings. Various atomic layer deposition (ALD), with layer thicknesses between 10 and 50 nm, and Parylene (polymeric) coatings, with layer thicknesses < 50 µm, are applied to stainless steel (1.4571) and structural steel (1.0038) substrates. The stability against critical thermal process conditions and cleaning media (acids, alkalis, solvents) is examined. The surface free energy of the substrates is determined before and after durability tests using a contact angle measuring device. In this study the targeted water contact angle was between 80° and 110° and the related surface free energy < 45 mN/m. The change in the surface free energy is a measure of the coating durability. The tested Parylene-coated substrates show no significant changes and no layer defects. In the case of the ALD-coated substrates, only the coating with TiO2 deposition using a chlorine-free precursor shows promising results. Non-systematical layer defects and corrosion can sometimes be optically observed on the TiO2 and Al2O3 ALD-coated substrates. A strong increase in the polar part of the surface free energy is observed. This may be due to the physisorption and chemisorption of water with the coating, increasing polar interactions. In further research, fouling experiments must be performed to investigate the influence of the coatings on the induction time. [ABSTRACT FROM AUTHOR]

The primary focus of this study is to assess the stripping resistance of bitumen when partially replaced with rice-straw biomass-based lignin from bio-ethanol industry residue. Moreover, the study examines the relationship between the chemical and physicochemical (surface free energy or SFE) properties of lignin-substituted bitumen blends and their stripping potential. Two distinct lignin materials were examined: fermentation residue (FRL), a by-product directly obtained from the bio-ethanol industry, and Isolated Lignin (IL), which was extracted from FRL through an alkali-acid precipitation process. These materials were partially substituted at dosages of 5%, 10%, and 15% by weight of bitumen. Test results indicated that the addition of lignin to bitumen led to a change in SFE, with an increase in the polar component and a reduction in the dispersive component. The rolling bottle test revealed that bitumen blends containing IL and FRL displayed superior stripping resistance compared to the base bitumen, retaining more coating after testing. This enhancement in performance was attributed to the increased heteroatom content [sum of nitrogen (N), oxygen (O), and sulfur (S)] and higher IS═O and IC═O indices upon adding the lignin materials. While the energy ratio obtained from the SFE alone did not entirely explain the stripping resistance of lignin-substituted bitumen, the presence of heteroatoms like N, O, and S, and the presence of silicon (Si) and associated functional groups played a substantial role in the chemical adhesion of these bitumen blends to aggregates. In conclusion, the incorporation of IL and FRL lignin materials holds promise for enhancing the stripping resistance of base bitumen. [ABSTRACT FROM AUTHOR]

Overland flow from inundation events (IEs) such as hurricanes or tsunamis produce destructive loading conditions on nearshore structures. The magnitude of this loading and its associated impact can be substantially reduced by the existence of natural and/or anthropogenic obstacles, such as planted vegetation patches or neighboring structures. This paper examines the shielding effects offered by onshore coastal vegetation to nearshore structures, by establishing a numerical framework in combination with statistical computing methods to explore how vegetation properties, such as density and, more important, geometry relative to a row of shoreline infrastructure elements, impacts the resultant IE loads and subsequently the structural vulnerability. Computational fluid dynamics (CFD) simulations are first conducted to predict the intensity measures (IMs) of interest (momentum flux, free surface elevation, water pressure, and depth-averaged velocities, as well as base shear forces) on the shoreline structures for different excitation intensities (wave heights) and vegetation configurations. This information is used to develop a predictive model for the IMs using surrogate modeling techniques in order to expedite the succeeding risk assessment process. Gaussian process (GP) regression is specifically adopted as the surrogate modeling technique here, since it can accommodate noise in the training observations (CFD numerical errors) and quantify the associated predictive uncertainty (originating from the surrogate model) with minimal additional computational complexity. The spatial correlation between some of the examined IMs is explicitly addressed at the GP calibration stage. The developed predictive model is then used to estimate the structural vulnerability, with the surrogate model prediction errors explicitly considered when calculating the probability of exceedance for the different damage states, as warranted in such a vulnerability setting. Comparisons among different vegetation configurations, including the bare earth case, support an in-depth exploration of the impact of vegetation geometry on the shielding effects it can offer. Two case studies are examined, demonstrating applicability of the proposed framework for both system- and component-level vulnerability assessments. [ABSTRACT FROM AUTHOR]

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The Amazon rainforest is a vital component of the global climate system, influencing the hydrological cycle and tropical circulation. However, understanding and modeling the evolution of convection in this region remain a scientific challenge. Here, we assess the environmental conditions associated with shallow, congestus, and isolated deep convection days during the wet season (December to April), employing measurements from the Green Ocean Amazon 2014–2015 (GoAmazon2014/5) experiment and large-scale wind fields from the constrained variational analysis. Composites of deep days show moister than average conditions below 3 km early in the morning. Analyzing the water budget at the surface through observations only, we estimated the water vapor convergence term as a residual of the water balance closure. Convergence remains nearly zero during the deep days until early afternoon (13:00 LST), when it becomes a dominant factor in the water budget. At 14:00 LST, the deep days experience a robust upward large-scale vertical velocity, especially above 4 km, which supports the shallow-to-deep convective transition occurring around 16:00–17:00 LST. In contrast, shallow and congestus days exhibit drier pre-convective conditions, along with diurnal water vapor divergence and large-scale subsidence that extend from the surface to the lower free troposphere. Moreover, afternoon precipitation exhibits the strongest linear correlation (0.6) with large-scale vertical velocity, nearly double the magnitude observed for other environmental factors, even moisture, at different levels and periods of the day. Precipitation also exhibits a moderate increase with low-level wind shear, while upper-level shear has a relatively minor negative impact on convection. [ABSTRACT FROM AUTHOR]

With field effect transistor (FET) sustained to downscale to sub‐10 nm nodes, performance degradation originates from short channel effects (SCEs) degradation and power consumption increment attributed to inhibition of supply voltage (VDD) scaling down proportionally caused by thermionic limit subthreshold swing (SS) (60 mV dec−1) pose substantial challenges for today's semiconductor industry. To further sustain the Moore's law life, incorporation of new device concepts or new materials are imperative. 2D materials are predicted to be able to combat SCEs by virtue of high carrier mobility maintainability regardless of thickness thinning down, dangling bonds free surface and atomic thickness, which contributes to super gate electrostatic controllability. To overcome increasing power dissipation problem, new device structures including negative capacitance FET (NCFET), tunnel FET (TFET), dirac source FET (DSFET) and the like, which show superiority in decreasing VDD by lowering SS below thermionic limit of 60 mV dec−1 have been brought out. The combination of 2D materials and ultralow steep slope device structures holds great promise for low power‐dissipation electronics, which encompass both suppressed SCEs and reduced VDD simultaneously, leading to improved device performance and lowered power dissipation. [ABSTRACT FROM AUTHOR]

Ice nucleation is a crucial process in nature and industries; however, the role of the free surface of water in this process remains unclear. To address this, we investigate the microscopic freezing process using brute-force molecular dynamics simulations. We discover that the free surface assists ice nucleation through an unexpected mechanism. The surface-induced negative pressure enhances the formation of local structures with a ring topology characteristic of Ice 0-like symmetry, promoting ice nucleation despite the symmetry differing from ordinary ice crystals. Unlike substrate-induced nucleation via water-solid interactions that occurs directly on the surface, this negative-pressure-induced mechanism promotes ice nucleation slightly inward the surface. Our findings provide a molecular-level understanding of the mechanism and pathway behind free-surface-induced ice formation, resolving the longstanding debate. The implications of our discoveries are of substantial importance in areas such as cloud formation, food technology, and other fields where ice nucleation plays a pivotal role. Ice nucleation is pivotal, yet the role of water's free surface remains unclear. Here, authors elucidate how the free surface aids ice nucleation through an unexpected mechanism involving negative pressure-induced formation of Ice 0-like structures. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) are a widely used technology for the treatment of wastewater, with Free Water Surface Constructed Wetlands (FWS CWs) being the simplest configuration. However, there is currently no consensus on the Hydraulic Retention Time (HRT) that optimizes P removal efficiency. To address this issue, this study conducted a bibliometric review of 85 scientific articles published between 1997 and 2021 that investigated the relationship between P removal and the HRT in FWS CWs. Scientometric maps were constructed to identify key topics, and bibliometric surveys were used to refine and explore the relationship between P removal and HRT. The analysis found a high correlation between P removal and HRT across all scales of the FWS CW systems, ranging from moderate to very strong. Specifically, the regressions between P removal efficiency and HRT were 73%, 70%, and 67% for lab-scale, pilot-scale, and real-scale systems, respectively. Overall, the FWS CWs demonstrated strong P removal efficiency, with removal rates reaching 95%, making them a promising technology for the tertiary treatment of effluents with a focus on nutrient removal and recovery. Future studies that focus on the many parameters of CW, especially on how macrophytes management affects the nutrient removal performance of these systems, are necessary to enrich our knowledge of CWs and optimize the application of this technology to wastewater treatment. [ABSTRACT FROM AUTHOR]

Thin films, bubbles and membranes are central to numerous natural and engineering processes, i.e., in solar cells, coatings, biosensors, foams, and emulsions. Yet, the characterization and understanding of their rupture is limited by the scarcity of atomic detail. We present here the complete life-cycle of freely suspended films using non-equilibrium molecular dynamics simulations of a simple atomic fluid free of surfactants and surface impurities, thus isolating the fundamental rupture mechanisms. We identified a short-term 'memory' by rewinding in time from a rupture event, extracting deterministic behaviors from apparent stochasticity. A comprehensive investigation of the key rupture-stages including both unrestrained and frustrated propagation is made—characterization of the latter leads to a first-order correction to the classical film-retraction theory. The highly resolved time window reveals that the different modes of the morphological development, typically characterized as nucleation and spinodal rupture, continuously evolve seamlessly with time from one into the other. The rupture of thin liquid films has mostly been studied for supported films, where the substrate creates ambiguity in identifying the processes at film level that lead to rupture. Focusing on spontaneous rupture, the authors portray the complete life-cycle of freely suspended films of pure liquid, corroborating that deterministic hole formation precedes the stochastic spontaneous rupturing of thin films. [ABSTRACT FROM AUTHOR]

In recent years, attention to the realization and characterization of wetsuits for scuba diving and other sea sports or activities has increased. The research has aimed to establish reliable and standardized measurement methods to objectively assess wetsuit quality, particularly focusing on their mechanical and thermal properties. In this work, we describe and compare two different measurement methods for the characterization of neoprene wetsuit thermal resistivity. The first method follows the existing regulations in the field, while the second one, which we are originally proposing in this paper, offers an alternative yet accurate way based on a simplified experimental set-up and easier measurements. In both cases, the wetsuit sample under testing was shaped in the form of a cylindrical sleeve of proper dimensions and wrapped around a phantom containing water at a higher temperature and surrounded by water at a lower temperature. The wetsuit's cylindrical surface allows heat flow from the warmer water on the inside to the colder water on the outside through the wetsuit area. In the first case, a thermal steady state was achieved, with constant heat flow from the phantom to the exterior. This was obtained with a power balance between two homogenous quantities. Electrically supplied thermal heating within the phantom was used to balance the thermal energy naturally flowing through the wetsuit's surface. In this first case, a stable and fixed temperature difference was obtained between the inner and the outer surfaces of the wetsuit sample. In the second case, a thermal transient was analyzed during the cooling process of the phantom, and the thermal time constant was measured, providing the sample thermal resistance once the phantom thermal capacity was known. In both cases and methods, the heat flow and thermal resistance of other elements than the wetsuit must be evaluated and compensated for if they are not negligible. Finally, the thermal resistivity per unit area of the wetsuit material was obtained with the product of the wetsuit sample's thermal resistance and the wetsuit area. The measurements, conducted until now by immersing the phantom in a free surface tank, show that both methods—under stationary and under transient temperature conditions—were valid to assess the wetsuit's thermal resistivity. The stationary method somehow provided better accuracy while involving less well-known parameters but at the expense of a more complicated experimental set-up and additional energy consumption. The transitory method, on the other hand, is quite easy to implement and, after careful characterization of the phantom's parameters, it provided similar results to the stationary one. An uncertainty budget was evaluated for both methods, and they did provide highly compatible measurement results, with resistivity values of 0.104(9) m2·K/W (stationary method) and 0.095(9) K·m2/W (transient method) for the same wetsuit sample under testing, which is also consistent with the values in the literature. We finally propose that the novel method is a valid alternative for characterization of the thermal insulation properties of a scuba diving wetsuit. [ABSTRACT FROM AUTHOR]

There have been ever more in-situ tunnel extension projects due to the growing demand for transportation. The traditional blast scheme requires a large quantity of explosive and the vibration effect is hard to control. In order to reduce explosive consumption and the vibration effect, an optimized non-cut blast scheme was proposed and applied to the in-situ expansion of the Gushan Tunnel. Refined numerical simulation was adopted to compare the traditional and optimized blast schemes. The vibration attenuation within the interlaid rock mass and the vibration effect on the adjacent tunnel were studied and compared. The simulation results were validated by the field monitoring of the vibration effect on the adjacent tunnel. Both the simulation and the monitoring results showed that the vibration velocity on the adjacent tunnel's back side was much smaller than its counterpart on the blast side, i.e., the presence of cavity reduced the blasting vibration effect significantly. The optimized non-cut blast scheme, which effectively utilized the existing free surface, could reduce the explosive consumption and vibration effect significantly, and might be preferred for in-situ tunnel expansion projects. [ABSTRACT FROM AUTHOR]

The depth dependence of structural relaxation dynamics is a key part of understanding thin glassy films. Despite this importance and decades of research, a method to provide this information has proved elusive. We measure the isothermal rejuvenation of stable glass films of poly(styrene), and demonstrate that the propagation of the front responsible for the transformation to a supercooled-liquid state serves as a highly localized probe of the local dynamics of the supercooled liquid. We use this connection to probe the depth-dependent relaxation rate with nanometric precision for a series of polystyrene films over a range of temperatures near the bulk glass transition temperature. The analysis shows the spatial extent of enhanced surface mobility and reveals the existence of an unexpected large dynamical length scale in the system. The results are compared with the cooperative-string model for glassy dynamics. The data reveals that the film-thickness dependence of whole film properties arises mainly from the volume fraction of the near-surface region. While the dynamics farthest from the free surface shows the expected bulk-like temperature dependence, the dynamics in the near-surface region shows very little dependence on temperature. This technique can be used in a broad range of thin film materials to gain previously unattainable information about localized structural relaxation. Measurements of depth dependent dynamics are a critical, and so far unattained, component of understanding the properties of thin glassy films. The authors describe the use of rejuvenation of stable glasses to achieve this goal, and apply it to the case of polystyrene glass. [ABSTRACT FROM AUTHOR]

The impact of droplets on the solid wall is a typical free surface flow phenomenon that widely exists in nature, industry, and daily life. According to the change of the droplet's center thickness, the droplet, the spreading process of the droplet is usually divided into three unique stages: the initial droplet deformation stage, the inertia-dominated stage, and the viscosity-dominated stage with the increase of the impact time. The problem of the liquid droplet spreading under different impact conditions is simulated by the smoothed particle hydrodynamics (SPH) method. Firstly, the dynamic process of droplet spreading is simulated and compared with relevant experimental results to verify the effectiveness of the proposed method. Then, the effects of the Weber number and the diameter ratio of the droplet to the curved wall surface on the droplet's maximum spreading diameter and central thickness were studied and analyzed. On this basis, the key coefficient in the existing relationship between the Weber number and maximum spreading diameter is fitted. Finally, the fitting equation of the center thickness and the impact time in the third stage of droplet spreading is assessed. [ABSTRACT FROM AUTHOR]

Building a lithium–sulfur (Li–S) battery with lean electrolytes is essential to far exceed the energy density of today's Li‐ion. However, earlier electrolyte depletion triggered by Li‐metal anodes (LMAs) causes sluggish Li–S redox kinetics and poor S utilization, resulting in a short cycle lifespan. To retard the electrolyte loss effectively, sustainable protection of LMAs is necessary against the dynamic interfacial evolution between LMA and protective layers (PLs). This study elucidates two critical parameters in securing the interfacial adaptivity of PLs upon local Li pitting: surface free energy (SFE) and Young's modulus through solid‐mechanic simulations and experiments using three different PL models. To alleviate the PL delamination at the early stage, a dual‐layer structured, adaptive protective layer (APL) is introduced to adapt the Li pitting‐driven structural evolution of the PL|LMA interfaces. The APL consists of a high‐ SFE polymer as an inner layer, reducing the interfacial energy in contact with LMA surface, and a highly stretchable polymer for outer shield, serving as a physical barrier for the electrolyte and Li polysulfides. APL‐coated LMA demonstrates stable cycling of Li–S cells, achieving a twofold extension of cycle‐life compared to unprotected LMA, even superior to other single‐layer PLs. [ABSTRACT FROM AUTHOR]

The Leidenfrost effect for a droplet on an over-heated substrate always results in a superhydrophobic state, significantly hindering the water evaporation for heat dissipation. Here, we demonstrate a strategy of air discharge assisted electrowetting-on-dielectrics (ADA-EWOD), overcoming this challenge. This strategy increases the solid surface free energy by generating air discharge near the three-phase contact line of the droplet and combines it with the electromechanical force to decrease the contact angle, which makes ADA-EWOD have stronger wetting capabilities than traditional electrically control methods that only rely on electromechanical force. The water contact angle on an over-heated surface (above 350 °C) is decreased from nearly 180° down to less than 10°. This superhydrophilicity at high temperature reduces the droplet lifetime by at least 10 times, well inhabiting the Leidenfrost effect. Furthermore, we use ADA-EWOD in droplet evaporation for heat dissipation, where a heated silicon wafer at 600 °C is cooled down to less than 200 °C within 20 s. We believe that the present work provides a perspective on suppressing the Leidenfrost effect, which may have important potential applications in the field of heat dissipation. [ABSTRACT FROM AUTHOR]

Free water surface constructed wetlands (FWSCWs) for the treatment of various wastewater types have evolved significantly over the last few decades. With an increasing need and interest in FWSCWs applications worldwide due to their cost-effectiveness and other benefits, this paper reviews recent literature on FWSCWs' ability to remove different types of pollutants such as nutrients (i.e., TN, TP, NH4-N), heavy metals (i.e., Fe, Zn, and Ni), antibiotics (i.e., oxytetracycline, ciprofloxacin, doxycycline, sulfamethazine, and ofloxacin), and pesticides (i.e., Atrazine, S-Metolachlor, imidacloprid, lambda-cyhalothrin, diuron 3,4-dichloroanilin, Simazine, and Atrazine) that may co-exist in wetland inflow, and discusses approaches for simulating hydraulic and pollutant removal processes. A bibliometric analysis of recent literature reveals that China has the highest number of publications, followed by the USA. The collected data show that FWSCWs can remove an average of 61.6%, 67.8%, 54.7%, and 72.85% of inflowing nutrients, heavy metals, antibiotics, and pesticides, respectively. Optimizing each pollutant removal process requires specific design parameters. Removing heavy metal requires the lowest hydraulic retention time (HRT) (average of 4.78 days), removing pesticides requires the lowest water depth (average of 0.34 m), and nutrient removal requires the largest system size. Vegetation, especially Typha spp. and Phragmites spp., play an important role in FWSCWs' system performance, making significant contributions to the removal process. Various modeling approaches (i.e., black-box and process-based) were comprehensively reviewed, revealing the need for including the internal process mechanisms related to the biological processes along with plants spp., that supported by a further research with field study validations. This work presents a state-of-the-art, systematic, and comparative discussion on the efficiency of FWSCWs in removing different pollutants, main design factors, the vegetation, and well-described models for performance prediction. [ABSTRACT FROM AUTHOR]

The presented paper investigates the creation of chitosan-based composites on the surface of chemically modified poly-D-lactic acid (PDLA). PDLA was dissolved in chloroform and cast into a glass dish until the complete evaporation of the solvent. The surface of the created PDLA films was modified with 1,6-hexanediamine and glutaraldehyde for the creation of free aldehyde side groups. Composite layers of chitosan (CH) were deposited on the surface of the modified films. The mechanical properties of the composite films were investigated using a dynamometer. The surface morphology of the created composite films was studied with Scanning electron microscopy (SEM). Sessile drop method was used to determine the surface free energy of the created chitosan-based composite layers. [ABSTRACT FROM AUTHOR]

Based on the nonlocal theory, a layered theoretical model is presented for vibration analysis of piezoelectric–piezomagnetic bimorph nanobeams. The layer-wise expressions of displacement and potential fields across the thickness are provided through ensuring the continuity of displacements and shear stresses at the interface as well as the shear stress free at the surface, and then the nonlocal governing equations and consistent boundary conditions are derived from the Hamilton's principle. For typical support conditions at beam ends, the differential quadrature method is developed to obtain the numerical results which is verified by comparing with analytical solutions for the simply-supported beam. A detailed parametric study is conducted to analyze the influence of nonlocal parameter, structure size, external load and boundary condition on the natural frequency and mode shape. It indicates the nonlocal small-scale effect should be considered to accurately predict the vibration properties of magnetoelectric laminated nanostructures. [ABSTRACT FROM AUTHOR]

This work analyzes the propagation of BG wave in a layered model composed of a piezo-flexo-magnetic (PFM) layer of finite width imperfectly bonded to a PFM half-space with consideration of impedance boundary at the free surface of layer. The flexo-magnetic phenomenon introduces loss which results in attenuation of propagating BG wave. Using suitable surface and interface conditions, a complex frequency equation is obtained, which relates real wave number with a complex form of wave velocity with the help of material, interface, impedance, and flexo-magnetic parameters. The dispersion and attenuation relations of BG waves are derived from separating this frequency relation into real and imaginary parts. These dispersion and attenuation equations relate wave number with phase and damp velocities, respectively. With the help of these relations, the phase/damp velocities are plotted against wave number illustrating the influence of interface imperfection parameter, the flexo-magnetic parameter corresponding to layer and half-space, impedance parameter, & layer width in magnetically short (MS) and magnetically open (MO) conditions. The impact of varying damp velocity on phase velocity and vice-versa is also portrayed in MS and MO cases. Some validation with previously existing literature is also provided. [ABSTRACT FROM AUTHOR]

Commercial hot‐dip galvanized zinc (Zn‐0.2% Al), galfan (Zn‐5% Al), and galvalume (Zn‐55% Al) coatings were exposed to wet scCO2, followed by an assessment of microstructural changes in the coating structure. Zinc and galfan coatings showed similar surface activity with abundant zinc dissolution and uniform corrosion product deposition. The Al‐rich phases of the galfan coating were intact in the studied atmosphere and eventually became embedded within the deposits. The zinc dissolution ended for zinc and galfan coatings when the free metal surface was blocked from the surrounding medium by a uniform corrosion product layer. Galvalume showed scarce reactivity: dissolution of zinc in the Zn‐rich interdendritic areas proceeded slowly compared to zinc and galfan, and the Al‐rich dendrites (with nm‐scale Zn inclusions) remained intact. The ion beam milling technique combined with modern nm‐resolution energy‐dispersive spectroscopy analysis enabled previously unseen visualization of the discussed corrosion processes. [ABSTRACT FROM AUTHOR]

We prove the existence of finite groups acting freely as orientation‐preserving homeomorphisms on closed orientable surfaces that extend as a group of homeomorphisms of some compact orientable 3‐manifold but that cannot extend to a handlebody. This solves a basic problem in low‐dimensional equivariant topology going back to the work of Reni and Zimmermann in the mid‐1990s. [ABSTRACT FROM AUTHOR]

The oxygen lance jet plays a crucial role in the steelmaking process in a converter. The quantitative relationship between the operating parameters of the oxygen lance and the volume of the impact cavity is established for the first time, and the leading factors affecting the volume of the impact cavity are identified through correlation analysis. This article examines the influence of operating pressure and lance position on the impact cavity of a 170 t converter in a nonisothermal environment through numerical analysis. The results show that the ambient temperature in the converter presents a layered phenomenon. The temperature near the free surface ranges from 1550 to 1600 K and then gradually decreases to 900 K at the oxygen lance outlet. When the ratio of the operating pressure to the design working pressure is less than 1.0 or greater than 1.3, the cavity volume is significantly affected by the operating pressure but has less of an impact when the ratio is between 1.0 and 1.3. The cavity volume shows a linear relationship with the oxygen lance position. Moreover, the oxygen lance position has a greater influence on the cavity volume and velocity distribution than do the operating pressure. [ABSTRACT FROM AUTHOR]

This work investigates the influence of couple stresses on intrinsic and extrinsic dislocations within three-dimensional heterogeneous multilayered structures. The materials consist of orthotropic and dissimilar layers with different elastic properties, incorporating the microstructural lengths from a special version of the anisotropic couple-stress elasticity. Double Fourier series expansions are used to describe extended displacements and tractions, considering rotation and couple-stress components and accounting for arbitrary displacement and rotation discontinuities associated with dislocation and disclination loops as well as periodic dislocation and disclination networks at semi-coherent interfaces. The dual-variable and position technique is used to recursively determine the field responses at any point in the multilayered laminate. The application examples focus on dislocation problems with couple stresses, revealing the effects of the core-spreading dislocation technique, free surfaces, anisotropic elasticity, and couple stresses on the field solutions. The analysis also uncovers pressure and von Mises stress amplitudes, non-zero rotation, and non-symmetric stress profiles due to couple stresses in copper/niobium bimaterials. Changes in the sign and magnitude of the Peach-Koehler forces are observed when couple stresses are introduced, which deviate from the classical theory of dislocations. The investigation finds a significant 29% reduction in energy per unit area at a semi-coherent interface between copper and niobium influenced by couple stresses. These results deepen our understanding of how couple stresses affect dislocation behavior in multilayered materials, and provide prospects for future discrete dislocation and disclination dynamics simulations with engineering applications in various nano- and micro-structured materials. • Novel solutions for dislocation and disclination loops in anisotropic composites. • The misfit dislocation network with couple stress is considered. • Solutions are provided by means of double Fourier series expansions. • Couple-stresses lead to a 29% reduction in energy at a semi-coherent Cu/Nb interface. [ABSTRACT FROM AUTHOR]

Convection across circular concentric gaps between cylinders is crucial in industrial applications, including electronic cooling, heat exchangers, and solar collectors. The effect of longitudinal and annular grooves on the outside surface of the inside tube on natural convective heat transmission in enclosure concentric circular annulus is experimentally investigated in the present work. Twin pairs of circular aluminum cylinders with the same radius ratio, length, and surface area were examined. Each one consists of two concentric circular cylinders. To maintain a steady heat flux, the inside cylinder of each pair has an electrical heater connected. The results indicate that the increases in the Nusselt number of around 25%, 43%, 67%, 123%, 142%, 157%, and 172% are seen for groove depths of 0.05 cm, 0.10 cm, 0.15 cm, 0.20 cm, 0.25 cm, 0.3 cm, 0.35 cm, and 0.4 cm. In addition, increasing the depth of the longitudinal groove raises the Nusselt number by roughly 33%, 51%, 79%, 99%, 136%, 153%, 173%, and 184%. The longitudinal grooves with a depth of 4.0 mm enable a 38% increase in free convection over prior research. An annular groove of 4.0 mm depth increases free convection by 36%. Furthermore, a further advancement over earlier research is attributable to the extensive surface contact area of the inner cylinder made possible by longitudinal or annular grooves. [ABSTRACT FROM AUTHOR]

Torricelli's law states that the speed of a fluid as it flows out of an orifice of a large reservoir open to the atmosphere is equal to 2 g h , where g is the acceleration of gravity and h is the distance between the free surface of the fluid in the reservoir and the orifice. Obtaining the flow rate from this speed is not at all trivial, despite how simple the situation seems, as the fluid jet issued at the orifice does not have a constant cross section and the motion of the fluid near the orifice is not really known. Here, we use Torricelli's experiment as a practical way to illustrate how to properly apply the momentum balance equation to solve hydrodynamic problems. We compare the horizontal component of the force exerted by the container on the fluid using both momentum conservation and the integral of the stress tensor; this results in a contradiction that we use to review, after considering simple experimental results, the assumptions made during the calculations, to finally resolve the discrepancy and rationalize the intricacies of this every-day situation. Editor's note: This paper shows how a familiar example from introductory fluid mechanics—the speed of a fluid as it exits a hole—contains subtleties that can be used to illustrate more advanced concepts in fluid mechanics. You'll want to adopt this as an example when you teach about control volumes. [ABSTRACT FROM AUTHOR]